From a Quasimolecular Band Insulator to a Relativistic Mott Insulator in t2g5 Systems with a Honeycomb Lattice Structure

Beom Hyun Kim, Tomonori Shirakawa, and Seiji Yunoki
Phys. Rev. Lett. 117, 187201 – Published 24 October 2016
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Abstract

The t2g orbitals of an edge-shared transition-metal oxide with a honeycomb lattice structure form dispersionless electronic bands when only hopping mediated by the edge-sharing oxygens is accessible. This is due to the formation of isolated quasimolecular orbitals (QMOs) in each hexagon, introduced recently by Mazin et al. [Phys. Rev. Lett. 109, 197201 (2012)], which stabilizes a band insulating phase for t2g5 systems. However, with the help of the exact diagonalization method to treat the electron kinetics and correlations on an equal footing, we find that the QMOs are fragile against not only the spin-orbit coupling (SOC) but also the Coulomb repulsion. We show that the electronic phase of t2g5 systems can vary from a quasimolecular band insulator to a relativistic Jeff=1/2 Mott insulator with increasing the SOC as well as the Coulomb repulsion. The different electronic phases manifest themselves in electronic excitations observed in optical conductivity and resonant inelastic x-ray scattering. Based on our calculations, we assert that the currently known Ru3+ and Ir4+ based honeycomb systems are far from the quasimolecular band insulator but rather the relativistic Mott insulator.

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  • Received 18 June 2016

DOI:https://doi.org/10.1103/PhysRevLett.117.187201

© 2016 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Beom Hyun Kim1,2, Tomonori Shirakawa3, and Seiji Yunoki1,2,3,4

  • 1Computational Condensed Matter Physics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
  • 2Interdisciplinary Theoretical Science (iTHES) Research Group, RIKEN, Wako, Saitama 351-0198, Japan
  • 3Computational Quantum Matter Research Team, RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
  • 4Computational Materials Science Research Team, RIKEN Advanced Institute for Computational Science (AICS), Kobe, Hyogo 650-0047, Japan

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Issue

Vol. 117, Iss. 18 — 28 October 2016

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